1. Field of the Invention
This invention relates to an inkjet head in which an ink repellent film having a high abrasion resistance is formed on the nozzle main body, a method for producing the same, and an inkjet recorder and an inkjet coater provided with the same.
2. Description of the Related Art
There have been developed various water repellent materials aiming at preventing adhesion of dirts, imparting waterproof property and so on. Concerning these water repellent materials, studies are mainly made on silicone materials and fluorinated materials. Compared with silicone materials, fluorinated materials are seemingly favorable in order to lower surface energy. Among fluorinated materials, compounds having perfluoroalkyl chain or compounds perfluoro polyether chain are mainly studied for forming monomolecular films, while fluorinated resins are mainly studied for forming polymer films.
These water repellent materials are employed in, for example, places where water is used such as kitchen and lavatory, automobile parts such as window and car body, office equipments such as display surface and inkjet head orifice surface, and so on.
Among all, inkjet printers, which are superior in downsizing suitability to electrophotographic printers, have been widely employed not only for office uses but also for household uses. In such an inkjet printer, an ink jetted from a nozzle head to printing paper alights to the paper, thereby forming an image.
When the ink clings around the nozzle in the orifice and dries during this process, the newly jetted ink comes into contact with the dried ink, which sometimes results in a change in the jetting direction. To overcome this problem, it is a common practice to subject the head surface in the ink jetting side to an ink repellent treatment. Also, a mechanism of wiping the nozzle surface is also employed.
As an example of related art, JP-A-2003-19803 proposes to treat the surface in the ink jetting side of a head with a compound having a perfluoro polyether chain and an alkoxysilane residue. According to this proposal, the thus treated head shows a high ink repellence and a high abrasion resistance in wiping in the case of using a water base ink. However, there is still a problem that no sufficient ink repellence or a sufficient abrasion resistance in wiping can be establish in the case of using an oil base ink or a solvent base ink.
JP-A-2003-341070 discloses to coat a nozzle forming member (in particular, the nozzle made of a resin material) with a fluorine base water-repellent agent and to form an SiO2 film between the nozzle forming member and the fluorine base water-repellent agent.
Although nozzle forming members made of resin materials are cited in the above example, it is desirable to use a metal material as the nozzle forming member from the viewpoint of the resistance against oil base inks and solvent base inks. Therefore, attempts are made to use a metal material as the nozzle-forming member and form an SiO2 film between the nozzle forming member and an ink repellent film. In this case, however, a sufficient ink repellence and a sufficient abrasion resistance during wiping can be established in some cases but not in other cases. Namely, constant effects cannot be obtained thereby. As the results of the subsequent studies aiming at further improving the performance, it is clarified that the treatment between the nozzle-forming member made of the metal material and the SiO2 film has a significant meaning.
JP-A-2004-34331 discloses a process which comprises preliminarily surface-roughening nozzle plate made of a resin or a metal having a glass transition temperature (Tg) of 100° C. or hither by the oxygen plasma treatment or a sand blasting treatment to give a surface roughness (Ra) of from 0.01 to 0.1, then forming a plasma polymer film of 0.5 μm or less on the thus roughened nozzle plate surface by the plasma CVD method with the use of a fluorine-containing compound or a silane compound as the starting material, and further applying a fluorinated resin on the film to give an ink repellent film. However, there has been known no treatment which is most suitable for forming an SiO2 film on a nozzle-forming member made of a metal material.
In recent years, application of the inkjet system to various patterning devices (for example, flat panel display production devices, three-dimensional modeling devices, print circuit board forming devices, fuel battery electrode forming devices and so on) have made rapid progress by taking advantage of the characteristics thereof. In these cases, use is made of not only water base inks but also oil base inks and solvent base inks. Moreover, inks containing organic resin components are sometimes employed therefor.
These inks have low surface tension, which sometimes causes some problems such that sufficient repellence cannot occur in an ink repellent film having a low ink repellence and an ink dries, solidifies and sticks around a nozzle. As the results of the inventors' studies, it is found out that the contact angle of the nozzle part of the head should be at least 40° in the case of oil base inks or solvent base inks.